As the Post‘s John Ivison reported three weeks ago, Justin Trudeau is seeking the Liberal leadership — which he almost certainly will win. Now that the rest of the Canadian media has caught up to the news, it’s a good time to ask whether the party’s 18th leader will be its last.

It’s fashionable to write off Mr. Trudeau as a lightweight, and his party as a spent force. But recent events in Quebec — specifically, Pauline Marois’ election as premier, and the student strikes that indirectly brought her separatist party to power — suggest there is an avenue for the Liberals, with Mr. Trudeau at the helm, to make themselves relevant again in Canadian politics, and perhaps even make a play for power.

First off, anyone who still dismisses Mr. Trudeau as an untested political dilettante isn’t paying attention. As early as 2006, he was chairing the Liberals’ youth-renewal task force. In 2008, he became an MP — and he did so in the competitive, highly multicultural, hardscrabble east-end Montreal riding of Papineau. In the 2008 election, he fought a hard door-to-door ground war against former BQ vice-president Vivian Barbot, defeating the incumbent by fewer than 1,200 votes. In 2011, he survived the Orange Wave, defeating his NDP challenger by more than 4,000 votes.

In short, he’s gone up against both the separatists, and the left, and won both times. Even if he’s done this using the political rocket juice of name recognition, he’s won the right not to be treated as a pretty-face novice.

Trudeau’s larger problem is (literally) existential: The Liberals don’t seem to have any reason for existence any more, no matter who is in charge. Under Jean Chrétien and Paul Martin, the Liberals were (or at least aspired to be) a big-tent, socially progressive, pro-gay, immigrant-welcoming, risk-averse welfare-state party that promotes sound governance, deficit control and free trade. But that’s exactly what the Conservatives have become. There can be only one.

Plus, the Conservatives have more energy and less fear when change to national policy is required — on, say, refugees, gun control, the wheat board, or foreign policy. That’s because the Conservatives aren’t burdened by the dead weight of the past. Unlike the Liberals, Stephen Harper and Jason Kenney don’t have to pay rhetorical homage to self-important “party of Laurier” claptrap every time they tie their shoes or brush their teeth.

But the Liberals do have one remaining advantage. As Conrad Black reminds us, the Liberals ruled Canada for 80 of the 110 years from 1896 onwards. And the reason for this, he argues, is that they were the party (a) that could convince Quebec to stay in Canada; and (b) that could convince the rest of Canada that they could make the sale in Quebec.

Yes, the sponsorship scandal temporarily destroyed this conceit. But Justin Trudeau’s Liberals may get a chance to reclaim the role. The BQ has collapsed, while the Tories — despite Mr. Harper’s outreach efforts — have become an unpopular stand-in for oilsands economics. As for Thomas Mulcair’s NDP, its stance on Quebec can only be described as farcically cynical: Any party that cannot give a full-throated defence of the Clarity Act is not a party that a single Canadian should trust to help keep Canada stitched together.

All of which is to say: Canada hasn’t had a politician who truly sold himself to both Quebec and the rest of Canada on a sustained basis since Jean Chrétien. It’s unclear if Justin Trudeau can do the job. But at least we know it’s a job that needs staffing — thus providing a solution to the Liberals’ existential crisis. And Mr. Trudeau’s success in Papineau (which is 45% French, 8% anglo, 47% none-of-the-above) suggests that he can get a wide variety of people to listen to him, including the young people who like to bang pots and pans.

Though many Canadians outside Quebec don’t realize it, we sit at a sensitive point in the history of our confederation. Yes, outright separatism remains a minority view in Quebec. But the province under Ms. Marois is embarking on a series of radical left-wing policies — including massive tax increases on the wealthy, a return to absurdly low college tuition (with student leaders now demanding that it be lowered to zero), and the sudden closing of the province’s only nuclear reactor. If Ms. Marois’ minority government survives for more than a few months, the result will be that Quebec comes to resemble a European nation ruled by a socialist-Green coalition. As the political gulf with the rest of the country grows, more and more Canadians will wonder why their equalization payments should be going to fund these sort of Scandinavian-style reveries. It will be separatism through the back door of socialism.

If the Liberals become relevant again, it likely will be because they offer some way to bridge this gulf — their traditional job in Canada. It’s a long shot. But stranger things have happened in Canadian politics.

In the wake of a Grammy Awards ceremony that disappointed many, from Kanye West to the masses on Twitter lamenting the state of pop music, a historical perspective is key. Few are better poised to offer one than Andy Kim.